Author + information
- Received November 12, 1993
- Revision received February 10, 1994
- Accepted February 17, 1994
- Published online July 1, 1994.
- David Keane, MB, MRCPI∗,
- Edward Boyd, PhD,
- David Anderson, FRCS,
- Alfonso Robles, MD,
- Philip Deverall, FRCS,
- Richard Morris, MSc,
- Graham Jackson, FRCP and
- Edgar Sowton, MD, FACC
- ↵∗Present address and address for correspondence: Dr. David Keane, Department of Interventional Cardiology, Thoraxcenter, Erasmus University, Room Ee 2332, P.O. Box 1738, Rotterdam 3000, The Netherlands.
Objectives. Because biphasic waveforms have previously been shown to be more efficient than monophasic waveforms in defibrillation of the ventricle, we compared the efficiency of the two waveforms in defibrillation of the atria.
Background. The development of an implantable atrial defibrillator would offer significant advantages over current approaches to the management of atrial fibrillation. Patient tolerance of atrial shocks from such a device, however, would depend critically on the deployment of an efficient waveform.
Methods. Both the monophasic and biphasic shocks were of 8-ms duration, and the biphasic was a dual-capacitor waveform with equal first- and second-phase duration and leading-edge voltage. One hundred randomized atrial shocks were evaluated in 21 patients during cardiopulmonary bypass. Atrial fibrillation was induced by the application of alternating current. Atrial shocks were delivered through customized, contoured epicardial paddles applied to the posterior left atrial wall (surface area 11 cm2) and to the anterior right atrial wall (surface area 26 cm2).
Results. For the monophasic waveform the delivered energy (joules) associated with 50% success (E50) was 1.44 J (95% confidence interval [CI] 0 to 11.2) and with 80% (E80) success 3.9 J (95% CI 2.42 to 109.8); for the biphasic waveform 50% success was achieved with 0.37 J (95% CI 0.36 to 0.38) (p = NS) and 80% success with 0.57 J (95% CI 0.56 to 0.58) (p < 0.05).
Conclusions. A biphasic waveform is more efficient than a monophasic waveform in atrial defibrillation. This may have implications for the development of an implantable atrial defibrillator for paroxysmal atrial fibrillation in addition to improvement of elective transthoracic and endocardial cardioversion of chronic atrial fibrillation.
- Received November 12, 1993.
- Revision received February 10, 1994.
- Accepted February 17, 1994.